US3738881A - Anisotropic etching of silicon and germanium - Google Patents
Anisotropic etching of silicon and germanium Download PDFInfo
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- US3738881A US3738881A US00182891A US3738881DA US3738881A US 3738881 A US3738881 A US 3738881A US 00182891 A US00182891 A US 00182891A US 3738881D A US3738881D A US 3738881DA US 3738881 A US3738881 A US 3738881A
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- silicon
- germanium
- etching
- oxidizing agent
- alcohol
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- 229910052710 silicon Inorganic materials 0.000 title abstract description 23
- 239000010703 silicon Substances 0.000 title abstract description 23
- 238000005530 etching Methods 0.000 title abstract description 22
- 229910052732 germanium Inorganic materials 0.000 title abstract description 20
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 title abstract description 20
- 239000007800 oxidant agent Substances 0.000 abstract description 22
- 238000000034 method Methods 0.000 abstract description 21
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 abstract description 12
- 230000015572 biosynthetic process Effects 0.000 abstract description 10
- 150000008044 alkali metal hydroxides Chemical class 0.000 abstract description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 abstract description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 21
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 18
- -1 aliphatic alcohols Chemical class 0.000 description 11
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 9
- 239000001089 [(2R)-oxolan-2-yl]methanol Substances 0.000 description 7
- BSYVTEYKTMYBMK-UHFFFAOYSA-N tetrahydrofurfuryl alcohol Chemical compound OCC1CCCO1 BSYVTEYKTMYBMK-UHFFFAOYSA-N 0.000 description 7
- 150000001298 alcohols Chemical class 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- QLOKJRIVRGCVIM-UHFFFAOYSA-N 1-[(4-methylsulfanylphenyl)methyl]piperazine Chemical compound C1=CC(SC)=CC=C1CN1CCNCC1 QLOKJRIVRGCVIM-UHFFFAOYSA-N 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 4
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 125000004432 carbon atom Chemical group C* 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 description 3
- 229910052700 potassium Inorganic materials 0.000 description 3
- 239000011591 potassium Substances 0.000 description 3
- DNIAPMSPPWPWGF-GSVOUGTGSA-N (R)-(-)-Propylene glycol Chemical compound C[C@@H](O)CO DNIAPMSPPWPWGF-GSVOUGTGSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
- 229910052792 caesium Inorganic materials 0.000 description 2
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 2
- 230000002939 deleterious effect Effects 0.000 description 2
- 150000004679 hydroxides Chemical class 0.000 description 2
- 125000004108 n-butyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 125000001453 quaternary ammonium group Chemical group 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 150000001299 aldehydes Chemical class 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- BTANRVKWQNVYAZ-UHFFFAOYSA-N butan-2-ol Chemical group CCC(C)O BTANRVKWQNVYAZ-UHFFFAOYSA-N 0.000 description 1
- 238000003486 chemical etching Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000000994 depressogenic effect Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000037230 mobility Effects 0.000 description 1
- 125000004123 n-propyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 125000001147 pentyl group Chemical group C(CCCC)* 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 1
- CPRMKOQKXYSDML-UHFFFAOYSA-M rubidium hydroxide Chemical class [OH-].[Rb+] CPRMKOQKXYSDML-UHFFFAOYSA-M 0.000 description 1
- PXLIDIMHPNPGMH-UHFFFAOYSA-N sodium chromate Chemical compound [Na+].[Na+].[O-][Cr]([O-])(=O)=O PXLIDIMHPNPGMH-UHFFFAOYSA-N 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/30604—Chemical etching
- H01L21/30608—Anisotropic liquid etching
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K13/00—Etching, surface-brightening or pickling compositions
- C09K13/04—Etching, surface-brightening or pickling compositions containing an inorganic acid
- C09K13/06—Etching, surface-brightening or pickling compositions containing an inorganic acid with organic material
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/10—Etching compositions
- C23F1/14—Aqueous compositions
- C23F1/32—Alkaline compositions
- C23F1/40—Alkaline compositions for etching other metallic material
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S148/00—Metal treatment
- Y10S148/051—Etching
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S148/00—Metal treatment
- Y10S148/115—Orientation
Definitions
- This invention relates to a technique for preferentially etching semiconductor material and to an etchant therefor. More particularly, the present invention relates to a technique for anisotropically etching silicon or germanium with an alkaline etchant in the presence of an oxidizing and a passivating agent.
- the present invention demonstrates that addition of an oxidizing agent of a suitable redox potential eliminates Patented June 12, 1973 SUMMARY OF THE INVENTION
- a novel etchant comprised of an alkaline aqueous solution, an oxidizing agent, and a passivating alcohol.
- the same etchant has also been found to etch germanium at a commercially practical rate, and with the same high degree of geometry control as achieved on silicon.
- the novel etchant described herein comprises (a) a strongly alkaline aqueous solution for rapid attack upon the (100) face of silicon (and of germanium if an oxidizing agent is simultaneously present), (b) a passivating alcohol which depresses the undesirably rapid etch rate of the planes, that is, two adjacent (211) faces as noted above, of silicon (or germanium in the presence of an oxidizing agent), and (c) an oxidizing agent which suppresses the formation of (111) sides pyramids on the (100) surface of silicon, and enables the etching of germanium to proceed.
- the strongly alkaline aqueous solutions alluded to hereinabove are typically selected from among the hydroxides of potassium and sodium. These materials have been found to be efficacious from a process standpoint and to be economically practical. However, the practice of the present invention is not limited thereto and other strongly alkaline agents such as the hydroxides of rubidium and cesium as well as quaternary ammonium hydroxides may be employed with equal efficacy.
- aliphatic alcohols as employed herein includes those unsubstituted alcohols having from 3 to 7 carbon atoms in the chain. Typical materials following within the scope of this definition are n-propyl, isopropyl, n-butyl, secondary butyl, tertiary butyl, pentyl, hexyl alcohols and the like. The limitations in the number of carbon atoms in the chain are dictated by practical considerations relative to solubility at the upper limit and marginal anisotropic etching at the lower limit.
- oxidizing agents may be selected from among potassium and sodium chromate.
- the oxidizing agent is employed in an amount ranging from 1-10 millimols per liter of etchant, such range being dictated by the observed reduction in pyramid density.
- the alcohols are employed in a concentration sufiicient to reduce the etch rate of the (110) plane.
- the etching procedure as described herein is conveniently conducted at a temperature within the range of 7090 C.
- EXAMPLE 1 Anisotropic etching of 4 ohm-centimeter, n-type germanium bearing a micropattern of sputtered photoresisted zirconium as an etching mask, was effected at 85 C. in an etchant comprising 4.5 normal potassium hydroxide, 0.2 normal tetrahydrofurfuryl alcohol and 20 milliliters of 30%hydrogen peroxide per liter of etchant. Etching was effected to a depth of 13 microns after 20 minutes, preferentially on the (100) surface of the germanium.
- Example 2 The procedure of Example 1 was repeated utilizing ohm-centimeter, n-type silicon. Etching was effected to a depth of microns after 20 minutes, preferentially on the 100) surface thereof. It is noted that the formation of the (111) sided pyramids, which normally tend to passivate the (100) surface prematurely, were eliminated.
- Example 3 The procedure of Example 2 was repeated with the exception that 10 millimols per liter of etchant of potassium chromate were substituted for the hydrogen peroxide. Etching was effected to a depth of 25 microns after 20 minutes, preferentially on the (100) surface of the silicon.
- EXAMPLE 4 The procedure of Example 3 was repeated wherein the tetrahydrofurfuryl alcohol was replaced first by n-propyl alcohol and subsequently by isopropyl, n-butyl, secondary butyl and tertiary butyl alcohol. Etching in each case was effected to a depth of approximately 25 microns over a 20-minute period, preferentially on the (10) surface. Again, it was noted that the formation of the deleterious pyramid was obviated by means of the described etchant.
- Technique for anistropic chemical etching of a monocrystalline semiconductor body selected from the group consisting of (100) oriented silicon and germanium which comprises applying to said semiconductor body carrying a suitable micropattern formed by an etch-resistant mask an etchant maintained at a temperature within the range of to C., said etchant comprising a solution of a hydroxide selected from the group consisting of potassium, sodium, cesium, quaternary ammonium and rubidium hydroxides, an oxidizing agent selected from the group consisting of hydrogen peroxide and potassium chromate and an alcohol selected from the group consisting of aliphatic unsubstituted alcohols having from 3 to 7 carbon atoms and tetrahydrofurfuryl alcohol, hydrogen peroxide being employed only in conjunction with tetrahydrofurfuryl alcohol, said oxidizing agent being employed in an amount ranging from one to ten millimols per liter of etchant.
- a hydroxide selected from the group consisting of potassium, sodium, cesium
- hydroxide is potassium hydroxide and said oxidizing agent is hydrogen peroxide.
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- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- General Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Weting (AREA)
- ing And Chemical Polishing (AREA)
Abstract
SINGLE CRYSTAL SILICON AND GERMANIUM HAVING MAJOR FACES PARALEL TO THE (100) PLANE MAY BE ETCHED ANISOTROPICALLY WITH AN ETCHANT COMPRISING AN OXIDIZING AGENT, AN ALCOHOL AND AN ALKALI METAL HYDROXIDE. IT HAS BEEN FOUND IN THE CASE OF SILICON THAT THE PRESENCE OF THE OXIDIZING AGENT IS NOT REQUIRED FOR ETCHING BUT INHIBITS THE FORMATION OF PYRAMIDS WHICH TERMINATE THE ETCHING PROCESS.
Description
United States Patent 3,738,881 ANISOTROPIC ETCHING OF SILICON AND GERMANIUM William Charles Erdman, Danielsville, and Paul Felix Schmidt, Allentown, Pa., assignors to Bell Telephone Laboratories, Incorporated, Murray Hill and Berkeley Heights, NJ. No Drawing. Filed Sept. 22, 1971, Ser. No. 182,891 Int. Cl. H011 7/50 US. Cl. 15617 6 Claims ABSTRACT OF THE DISCLOSURE Single crystal silicon and germanium having major faces parallel to the (100) plane may be etched anisotropically with an etchant comprising an oxidizing agent, an alcohol and an alkali metal hydroxide. It has been found in the case of silicon that the presence of the oxidizing agent is not required for etching but inhibits the formation of pyramids which terminate the etching process.
BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to a technique for preferentially etching semiconductor material and to an etchant therefor. More particularly, the present invention relates to a technique for anisotropically etching silicon or germanium with an alkaline etchant in the presence of an oxidizing and a passivating agent.
(2) Description of the prior art Semiconductor devices, whether of the single element or integrated circuit type, are fabricated universally from monocrystalline material in slice form. In both the single element and integrated device fabrication, precise removal of portions of the material is an important aspect of the process. For modern integrated circuit applications, geometry control of the etch pattern has acquired paramount importance. For the air gap insulation process, in particular, it is necessary to separate the individual chips or components of the circuit from each other, and to do this in a manner which sacrifices the least amount of valuable silicon surface in order to arrive at a high density of devices per unit area.
It has been known for some time that the (111) plane of silicon etches more slowly than the (100) or (110) planes in alkaline aqueous solution, and further, that the etch rate of the (110) plane (or more properly speaking, of two adjacent (211) planes, which crystallographically are very close to the (110) plane can be depressed by the addition of aliphatic alcohols, of which isopropyl or nbutyl alcohol are typical examples. Thus, when a (100) oriented siliconslice is etched in hot alkaline solution in the presence of an aliphatic alcohol, precise control over the geometry of the pattern to be etched is obtained.
'Until now this process on (100) oriented silicon was severely hindered by a premature termination of the etching action due to the formation of innumerable (111) sided pyramids on the (100) surface undergoing etching, the etch rate of the (111) faces being extremely low.
Heretofore, reports have not appeared in the literature relative to the anistropic etching of germanium. At the present time, silicon is generally preferred by industry because of the higher operating temperatures of devices made from silicon compared to those from germanium. However, carrier mobilities in germanium are considerably higher than in silicon, and for high frequency devices, germanium substrates will always be of interest.
The present invention demonstrates that addition of an oxidizing agent of a suitable redox potential eliminates Patented June 12, 1973 SUMMARY OF THE INVENTION In accordance with the present invention, the prior art limitations for precise geometry control in the etching of oriented silicon have been successfully obviated by utilizing a novel etchant comprised of an alkaline aqueous solution, an oxidizing agent, and a passivating alcohol. The same etchant has also been found to etch germanium at a commercially practical rate, and with the same high degree of geometry control as achieved on silicon.
DETAILED DESCRIPTION The novel etchant described herein comprises (a) a strongly alkaline aqueous solution for rapid attack upon the (100) face of silicon (and of germanium if an oxidizing agent is simultaneously present), (b) a passivating alcohol which depresses the undesirably rapid etch rate of the planes, that is, two adjacent (211) faces as noted above, of silicon (or germanium in the presence of an oxidizing agent), and (c) an oxidizing agent which suppresses the formation of (111) sides pyramids on the (100) surface of silicon, and enables the etching of germanium to proceed.
The strongly alkaline aqueous solutions alluded to hereinabove are typically selected from among the hydroxides of potassium and sodium. These materials have been found to be efficacious from a process standpoint and to be economically practical. However, the practice of the present invention is not limited thereto and other strongly alkaline agents such as the hydroxides of rubidium and cesium as well as quaternary ammonium hydroxides may be employed with equal efficacy.
With respect to the selection of passivating and oxidizing agents, the interrelationship therebetween must first be considered. Thus, it is known that alcohols can be readily oxidized to aldehydes or ketones; however, the ease with which any specific alcohol will be oxidized is dependent upon its chemical structure, aromatic alcohols being more stable than aliphatic alcohols and long chain aliphatic alcohols being more stable than short chain aliphatic alcohols. It has been determined with respect to silicon that the redox potential must be sufficiently high to prevent the formation of (111) sided pyramids on the (100) surface but not so high as to cause the passivating alcohol to oxidize rapidly. The same considerations apply with respect to germanium with the additional requirement that the redox potential of the oxidizing agent be high enough to enable rapid attack of the 100) surface of germanium in hot alkaline solution. Since the formation of the (111) sided pyramids on the (100) surface of silicon appears to be attributed to the action of hydrogen (which results from the dissolution reaction of silicon with water) and since germanium is only slightly more noble than hydro gen, these requirements are satisfied by selecting an oxidizing agent which is strong enough to oxidize hydrogen but not strong enough to oxidize the alcohol selected at an unduly rapid rate. In light of the fact that the oxidation resistance of the various alcohols varies over a considerable range, the type and concentration of oxidizing agent selected can also vary over a wide range.
Turning now to a consideration of specific combinations of passivating alcohol and oxidizing agent it has been found that the chromate ion in combination with aliphatic alcohols, and hydrogen peroxide in combination with tetrahydrofurfuryl alcohol are satisfactory. With respect to silicon, it has been determined that aliphatic alcohols are more suitable as passivating agents for the (1110) plane than aromatic alcohols and that the chromate ion fulfills the role of preventing pyramid formation without attacking the aliphatic alcohol at an appreciable rate. Hydrogen peroxide, a stronger oxidizing medium than chromate ion is suitable in combination with tetrahydrofurfuryl alcohol and unsatisfactory with the aliphatic alcohols because of the rapid rate of attack thereon. The same considerations obtain with respect to germanium.
The term aliphatic alcohols as employed herein includes those unsubstituted alcohols having from 3 to 7 carbon atoms in the chain. Typical materials following within the scope of this definition are n-propyl, isopropyl, n-butyl, secondary butyl, tertiary butyl, pentyl, hexyl alcohols and the like. The limitations in the number of carbon atoms in the chain are dictated by practical considerations relative to solubility at the upper limit and marginal anisotropic etching at the lower limit.
In addition to hydrogen peroxide, oxidizing agents may be selected from among potassium and sodium chromate.
In the practice of the present invention, the oxidizing agent is employed in an amount ranging from 1-10 millimols per liter of etchant, such range being dictated by the observed reduction in pyramid density. The alcohols are employed in a concentration sufiicient to reduce the etch rate of the (110) plane. The etching procedure as described herein is conveniently conducted at a temperature within the range of 7090 C.
Examples of the application of the present invention are set forth below. They are intended merely as illustrations and it is to be appreciated that the methods described may be varied by one skilled in the art without departing from the spirit and scope of the invention.
EXAMPLE 1 Anisotropic etching of 4 ohm-centimeter, n-type germanium bearing a micropattern of sputtered photoresisted zirconium as an etching mask, was effected at 85 C. in an etchant comprising 4.5 normal potassium hydroxide, 0.2 normal tetrahydrofurfuryl alcohol and 20 milliliters of 30%hydrogen peroxide per liter of etchant. Etching was effected to a depth of 13 microns after 20 minutes, preferentially on the (100) surface of the germanium.
EXAMPLE 2 The procedure of Example 1 was repeated utilizing ohm-centimeter, n-type silicon. Etching was effected to a depth of microns after 20 minutes, preferentially on the 100) surface thereof. It is noted that the formation of the (111) sided pyramids, which normally tend to passivate the (100) surface prematurely, were eliminated.
For comparative purposes, the procedure of this example was repeated in the absence of hydrogen peroxide, the oxidizing agent, it was observed that the formation of the deleterious pyramid caused passivation of the (100) surface and termination of etching process.
4 EXAMPLE 3 The procedure of Example 2 was repeated with the exception that 10 millimols per liter of etchant of potassium chromate were substituted for the hydrogen peroxide. Etching was effected to a depth of 25 microns after 20 minutes, preferentially on the (100) surface of the silicon.
EXAMPLE 4 The procedure of Example 3 was repeated wherein the tetrahydrofurfuryl alcohol was replaced first by n-propyl alcohol and subsequently by isopropyl, n-butyl, secondary butyl and tertiary butyl alcohol. Etching in each case was effected to a depth of approximately 25 microns over a 20-minute period, preferentially on the (10) surface. Again, it was noted that the formation of the deleterious pyramid was obviated by means of the described etchant.
What is claimed is:
1. Technique for anistropic chemical etching of a monocrystalline semiconductor body selected from the group consisting of (100) oriented silicon and germanium, which comprises applying to said semiconductor body carrying a suitable micropattern formed by an etch-resistant mask an etchant maintained at a temperature within the range of to C., said etchant comprising a solution of a hydroxide selected from the group consisting of potassium, sodium, cesium, quaternary ammonium and rubidium hydroxides, an oxidizing agent selected from the group consisting of hydrogen peroxide and potassium chromate and an alcohol selected from the group consisting of aliphatic unsubstituted alcohols having from 3 to 7 carbon atoms and tetrahydrofurfuryl alcohol, hydrogen peroxide being employed only in conjunction with tetrahydrofurfuryl alcohol, said oxidizing agent being employed in an amount ranging from one to ten millimols per liter of etchant.
2. Technique in accordance with claim 1 wherein said hydroxide is potassium hydroxide and said oxidizing agent is hydrogen peroxide.
3. Technique in accordance with claim 1 wherein said hydroxide is potassium hydroxide and said oxidizing agent is potassium chromate.
4. Technique in accordance with claim 1 wherein said hydroxide is sodium hydroxide and said oxidizing agent is potassium chromate.
5. Technique in accordance with claim 2 wherein said alcohol is tetrahydrofurfuryl alcohol.
6. Technique in accordance with claim 3 wherein said alcohol is n-propyl alcohol.
References Cited UNITED STATES PATENTS JACOB H. STEINBERG, Primary Examiner US. Cl. X.R. 25279.4, 79.5
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US18289171A | 1971-09-22 | 1971-09-22 |
Publications (1)
Publication Number | Publication Date |
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US3738881A true US3738881A (en) | 1973-06-12 |
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Application Number | Title | Priority Date | Filing Date |
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US00182891A Expired - Lifetime US3738881A (en) | 1971-09-22 | 1971-09-22 | Anisotropic etching of silicon and germanium |
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Country | Link |
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US (1) | US3738881A (en) |
JP (1) | JPS5212060B2 (en) |
KR (1) | KR780000484B1 (en) |
BE (1) | BE789090A (en) |
CA (1) | CA954425A (en) |
CH (1) | CH582755A5 (en) |
DE (1) | DE2245809C3 (en) |
FR (1) | FR2153384B1 (en) |
GB (1) | GB1357831A (en) |
IT (1) | IT969438B (en) |
NL (1) | NL166361C (en) |
SE (1) | SE380543B (en) |
Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3990925A (en) * | 1975-03-31 | 1976-11-09 | Bell Telephone Laboratories, Incorporated | Removal of projections on epitaxial layers |
US4013502A (en) * | 1973-06-18 | 1977-03-22 | Texas Instruments Incorporated | Stencil process for high resolution pattern replication |
DE2653901A1 (en) * | 1975-12-05 | 1977-06-08 | Ibm | POLISHING COMPOUND AND METHOD FOR SEMICONDUCTOR SUBSTRATE |
FR2372904A1 (en) * | 1976-11-19 | 1978-06-30 | Ibm | STRIPPING COMPOSITION OF POLYCRYSTALLINE SILICON CONTAINING TETRAMETHYLAMMONIUM HYDROXIDE AND APPLICATION METHOD |
US4172005A (en) * | 1976-10-21 | 1979-10-23 | Tokyo Shibaura Electric Co., Ltd. | Method of etching a semiconductor substrate |
US4680243A (en) * | 1985-08-02 | 1987-07-14 | Micronix Corporation | Method for producing a mask for use in X-ray photolithography and resulting structure |
US4918030A (en) * | 1989-03-31 | 1990-04-17 | Electric Power Research Institute | Method of forming light-trapping surface for photovoltaic cell and resulting structure |
US4996627A (en) * | 1989-01-30 | 1991-02-26 | Dresser Industries, Inc. | High sensitivity miniature pressure transducer |
US5116464A (en) * | 1989-06-02 | 1992-05-26 | Massachusetts Institute Of Technology | Cesium hydroxide etch of a semiconductor crystal |
US5431777A (en) * | 1992-09-17 | 1995-07-11 | International Business Machines Corporation | Methods and compositions for the selective etching of silicon |
US6114248A (en) * | 1998-01-15 | 2000-09-05 | International Business Machines Corporation | Process to reduce localized polish stop erosion |
US20050239673A1 (en) * | 2002-06-07 | 2005-10-27 | Hsu Chien-Pin S | Microelectronic cleaning compositions containing oxidizers and organic solvents |
US20110104875A1 (en) * | 2009-10-30 | 2011-05-05 | Wojtczak William A | Selective silicon etch process |
Families Citing this family (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6060237A (en) * | 1985-02-26 | 2000-05-09 | Biostar, Inc. | Devices and methods for optical detection of nucleic acid hybridization |
US5482830A (en) * | 1986-02-25 | 1996-01-09 | Biostar, Inc. | Devices and methods for detection of an analyte based upon light interference |
DE3805752A1 (en) * | 1988-02-24 | 1989-08-31 | Fraunhofer Ges Forschung | ANISOTROPIC ETCHING PROCESS WITH ELECTROCHEMICAL ETCH STOP |
US5639671A (en) * | 1989-09-18 | 1997-06-17 | Biostar, Inc. | Methods for optimizing of an optical assay device |
AU6513790A (en) * | 1989-09-18 | 1991-04-18 | Biostar Medical Products, Inc. | Apparatus for detection of an immobilized analyte |
US5541057A (en) * | 1989-09-18 | 1996-07-30 | Biostar, Inc. | Methods for detection of an analyte |
US5955377A (en) * | 1991-02-11 | 1999-09-21 | Biostar, Inc. | Methods and kits for the amplification of thin film based assays |
US5550063A (en) * | 1991-02-11 | 1996-08-27 | Biostar, Inc. | Methods for production of an optical assay device |
US5418136A (en) * | 1991-10-01 | 1995-05-23 | Biostar, Inc. | Devices for detection of an analyte based upon light interference |
US5494829A (en) * | 1992-07-31 | 1996-02-27 | Biostar, Inc. | Devices and methods for detection of an analyte based upon light interference |
US5552272A (en) * | 1993-06-10 | 1996-09-03 | Biostar, Inc. | Detection of an analyte by fluorescence using a thin film optical device |
US8021483B2 (en) | 2002-02-20 | 2011-09-20 | Hemlock Semiconductor Corporation | Flowable chips and methods for the preparation and use of same, and apparatus for use in the methods |
US6874713B2 (en) | 2002-08-22 | 2005-04-05 | Dow Corning Corporation | Method and apparatus for improving silicon processing efficiency |
US7270706B2 (en) | 2004-10-04 | 2007-09-18 | Dow Corning Corporation | Roll crusher to produce high purity polycrystalline silicon chips |
US9873833B2 (en) * | 2014-12-29 | 2018-01-23 | Versum Materials Us, Llc | Etchant solutions and method of use thereof |
-
0
- BE BE789090D patent/BE789090A/en unknown
-
1971
- 1971-09-22 US US00182891A patent/US3738881A/en not_active Expired - Lifetime
-
1972
- 1972-05-19 CA CA142,580A patent/CA954425A/en not_active Expired
- 1972-09-11 SE SE7211667A patent/SE380543B/en unknown
- 1972-09-16 KR KR7201398A patent/KR780000484B1/en active
- 1972-09-18 NL NL7212612.A patent/NL166361C/en not_active IP Right Cessation
- 1972-09-19 IT IT52846/72A patent/IT969438B/en active
- 1972-09-19 DE DE2245809A patent/DE2245809C3/en not_active Expired
- 1972-09-21 CH CH1382072A patent/CH582755A5/xx not_active IP Right Cessation
- 1972-09-21 GB GB4367272A patent/GB1357831A/en not_active Expired
- 1972-09-21 FR FR7233501A patent/FR2153384B1/fr not_active Expired
- 1972-09-21 JP JP47094188A patent/JPS5212060B2/ja not_active Expired
Cited By (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4013502A (en) * | 1973-06-18 | 1977-03-22 | Texas Instruments Incorporated | Stencil process for high resolution pattern replication |
US3990925A (en) * | 1975-03-31 | 1976-11-09 | Bell Telephone Laboratories, Incorporated | Removal of projections on epitaxial layers |
DE2653901A1 (en) * | 1975-12-05 | 1977-06-08 | Ibm | POLISHING COMPOUND AND METHOD FOR SEMICONDUCTOR SUBSTRATE |
US4172005A (en) * | 1976-10-21 | 1979-10-23 | Tokyo Shibaura Electric Co., Ltd. | Method of etching a semiconductor substrate |
FR2372904A1 (en) * | 1976-11-19 | 1978-06-30 | Ibm | STRIPPING COMPOSITION OF POLYCRYSTALLINE SILICON CONTAINING TETRAMETHYLAMMONIUM HYDROXIDE AND APPLICATION METHOD |
US4113551A (en) * | 1976-11-19 | 1978-09-12 | International Business Machines Corporation | Polycrystalline silicon etching with tetramethylammonium hydroxide |
US4680243A (en) * | 1985-08-02 | 1987-07-14 | Micronix Corporation | Method for producing a mask for use in X-ray photolithography and resulting structure |
US4996627A (en) * | 1989-01-30 | 1991-02-26 | Dresser Industries, Inc. | High sensitivity miniature pressure transducer |
US4918030A (en) * | 1989-03-31 | 1990-04-17 | Electric Power Research Institute | Method of forming light-trapping surface for photovoltaic cell and resulting structure |
US5116464A (en) * | 1989-06-02 | 1992-05-26 | Massachusetts Institute Of Technology | Cesium hydroxide etch of a semiconductor crystal |
US5431777A (en) * | 1992-09-17 | 1995-07-11 | International Business Machines Corporation | Methods and compositions for the selective etching of silicon |
US5565060A (en) * | 1992-09-17 | 1996-10-15 | International Business Machines Corporation | Methods and compositions for the selective etching of silicon |
US6114248A (en) * | 1998-01-15 | 2000-09-05 | International Business Machines Corporation | Process to reduce localized polish stop erosion |
US20050239673A1 (en) * | 2002-06-07 | 2005-10-27 | Hsu Chien-Pin S | Microelectronic cleaning compositions containing oxidizers and organic solvents |
US7419945B2 (en) * | 2002-06-07 | 2008-09-02 | Mallinckrodt Baker, Inc. | Microelectronic cleaning compositions containing oxidizers and organic solvents |
US20110104875A1 (en) * | 2009-10-30 | 2011-05-05 | Wojtczak William A | Selective silicon etch process |
US7994062B2 (en) | 2009-10-30 | 2011-08-09 | Sachem, Inc. | Selective silicon etch process |
Also Published As
Publication number | Publication date |
---|---|
KR780000484B1 (en) | 1978-10-24 |
FR2153384B1 (en) | 1976-10-29 |
JPS5212060B2 (en) | 1977-04-04 |
JPS4840380A (en) | 1973-06-13 |
GB1357831A (en) | 1974-06-26 |
BE789090A (en) | 1973-01-15 |
DE2245809C3 (en) | 1978-04-27 |
NL7212612A (en) | 1973-03-26 |
FR2153384A1 (en) | 1973-05-04 |
DE2245809B2 (en) | 1977-09-01 |
CH582755A5 (en) | 1976-12-15 |
DE2245809A1 (en) | 1973-04-05 |
NL166361B (en) | 1981-02-16 |
IT969438B (en) | 1974-03-30 |
CA954425A (en) | 1974-09-10 |
SE380543B (en) | 1975-11-10 |
NL166361C (en) | 1981-07-15 |
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